Purpose

To help students understand that some insects depend on dead plant material for food and they interact with other organisms in various ways.

Context

This lesson is the second of a two-part series on the cycle of life. This series should help enhance student understanding of the flow of matter and energy and the interdependence of life by focusing on food chains and food webs.

Cycle of Life 1: Food Chains focuses on the food chain by helping students understand that almost all kinds of animals’ food can be traced back to plants and that the sun is often the ultimate source of energy needed for all organisms to stay alive and grow.

This lesson gives students the opportunity to learn about food chains. Learning about a variety of food chains in various environments will help students learn to identify similarities and differences among them. For example, they will learn that materials can be recycled and used again, sometimes in different forms. Also, they will notice that substances may change form and move from place to place, but they never appear out of nowhere and never just disappear. It is important to note that although this lesson focuses on food chains of what eats what in various environments, it does not focus on labeling the steps in the chain as energy transfer. Transfers of energy at this level are better illustrated in physical systems; biological energy transfer is far too complicated.

Cycle of Life 2: Food Webs extends this thinking by focusing on how some insects depend on dead plant matter for food and incorporates ideas previously learned about food chains and food webs.

Students will explore how various organisms satisfy their needs in the environments in which they are typically found. In addition, they will examine the survival needs of different organisms and consider how the conditions in particular habitats can limit what kinds of living things can survive. These activities will help students understand the great diversity of life in different habitats.

Students finishing the second grade should understand that plants and animals need water to survive. In addition, they should know that animals need food to survive while plants need light. They also should understand that animals eat plants or other animals for food, and animals may also use plants (or even other animals) for shelter and nesting.

This prerequisite knowledge will help elementary students expand their knowledge to learn that almost all kinds of animals’ food can be traced back to plants and that some source of energy is needed for all organisms to stay alive and grow. They also should be able to expand their knowledge to learn that insects and various other organisms depend on dead plant material for food.

Planning Ahead

Note: If items are not easily available from the school’s science department, have students bring in one or all the items except the lamp (students can share the lamp(s) if necessary). They should probably have all items to you a week prior to the activity to make sure all items are available.

Motivation

Now students should use their student esheet to watch part of the interactive slideshow Let’s Talk about Insects, on the Urban Programs Resource Network website. (Note: The link listed will take students to slide 35; they should view only slides 35-43.)

Pose the following questions to students to stimulate their thinking about insects, the food they eat, and the environment in which they are typically found. These questions are intended to get students thinking for a project in the Development section, thus you do not need to have students write down their answers.

Do you think that each type of insect plays a specific role in its environment?

Do you think that you could move an insect that typically lives in a warm environment to a cold environment and expect that it would survive?

Do you think that there are other insects besides ants and termites that depend on dead plants for food?

Do you think that the extinction of a specific type of insect would upset the ecosystem?

Do you think that each type of insect is beneficial to our environment?

Answers will vary. Encourage students to explain their answers.

Development

In this part of the lesson, students will explore insects by doing a hands-on activity and conducting some research.

Students will explore what types of insects live under, on, and around dead trees! If there is an area on the school grounds, this can be done as a classroom activity. If not, students should do this activity outside of school in groups or individually with parents. If students do this activity outside of school, they can use the activity sheet to help guide them and their parents (you may want to provide a letter home to parents to explain what is expected of their children).

It would be great to point out that the log encompasses the entire cycle of life: the dead tree provides food and a home for insects, creatures, and plants that, in turn, help the tree to decompose into soil from which new trees will grow. At this point, students should write down other things they notice about the log and a standing dead tree if one is around (e.g., number of holes, sizes of holes, or other animals that may have inhabited the tree like birds or squirrels).

Once students have finished with the activity, they should select an insect that feeds off dead trees/debris. Using the Insects in Their Environment student esheet, students should get a picture of their insect and do some research on it using the Insect Explorers research sheet as a guide. Some sites on insects that may be helpful are:

Assessment

Students should write a paragraph or two regarding how insects and other organisms depend on dead plant and animal material for food and how they interact with one another. Their writing sample should include information such as:

Trees eventually die, and then fall down.

Insects, animals, and bacteria that feed and live off dead trees inhabit the trees and continue to live in them as they fall down and decay.

On the ground, once a dead tree becomes hollow, it might become a home for animals, such as a den of rabbits or foxes.